COOLING DRUM FOR CASTING THIN CAST PIECES AND METHOD AND APPARATUS FOR FORMING DIMPLES IN PERIPHERAL SURFACE OF THE DRUM

摘要

A cooling drum (1) for use in casting a thin cast strip is rotated about its axis while a laser beam (10a) of a wavelength of from 0.30 .mu.m to 1.07 .mu.m is irradiated onto a peripheral surface of the drum to form dimple (2) therein. At this time, at least one of the oscillation period of the laser beam, the laser output and the divergence angle of the beam is controlled to assure that each dimple (2) has a depth of not less than 50 .mu.m and a diameter of less than 500 .mu.m and the distance measured between the centers of each adjacent pair of dimples ranges from 1.05 times to 5 times the dimple diameter. At least one of the steps of adjusting the oscillation period of the laser beam and causing the laser beam to scan the peripheral surface of the drum in the axial direction thereof is conducted to cause a irregular deviation of less than 20% in the density of distribution of the thus formed dimples (2), whereby the formation of waves (5) in the surface of the molten metal (4) placed in contact with the drum (1) during the casting of the thin cast piece is suppressed, to thereby assure a continuous casting of thin cast piece having good surface characteristics and condition.